Base Station, Mobile Station, Communication System, Transmission Method and Reordering Method

1. A data delivery method of sending data and a sequence number corresponding to the data from a base station to a mobile station, and performing in order delivery of the data received by the mobile station based on the sequence number; comprising: differentiating, at a source base station, a first sequence number added to data that is transmitted to the mobile station from the source base station from a second sequence number added to data that is transmitted to the mobile station from a host station via a target base station and notifying the second sequence number to the target base station; adding, at the target base station, the second sequence number notified from the source base station to the data that is received from the host station and transmitting the data to which the second sequence number is added to the mobile station from the target base station; and at the mobile station, performing in order delivery of the data received from the source base station and the data received from the target base station using the sequence numbers.

2. A communication system for sending data and a sequence number corresponding to the data from a base station to a mobile station, and performing in order delivery of the data received by the mobile station based on the sequence number; comprising: a source base station; and a target base station wherein the source base station includes a processor that differentiates a first sequence number added to data that is transmitted to the mobile station from the source base station from a second sequence number added to data that is transmitted to the mobile station from a host station via the target base station and notifying the second sequence number to the target base station; wherein the target base station includes a processor that adds the second sequence number notified from the source base station to the data that is received from the host station and a transmitter that transmits the data to which the second sequence number is added to the mobile station; and the mobile station includes a data delivery processor that performs in order delivery of the data received from the source base station and the data received from the target base station using the sequence numbers.

3. A mobile station, comprising: a receiver that receives a first sequence number with data from a source base station and receives a second sequence number with data from a target base station in which the source base station differentiates the first sequence number added to the data that is transmitted to the mobile station from the source base station from the second sequence number added to data that is transmitted to the mobile station from a host station via the target base station and notifies the second sequence number to the target base station, and the target base station adds the second sequence number notified from the source base station to the data that is received from the host station and transmits the data to which the second sequence number is added to the mobile station; and a data delivery processor that performs in order delivery of the data received from the source base station and the data received from the target base station using the sequence numbers.

4. A base station comprising: a receiver that receives data from a host station; a processor that adds a second sequence number notified from a source base station to the data that is transmitted from the host station and received by the receiver in which the source base station differentiates a first sequence number added to data that is transmitted to a mobile station from the source base station from the second sequence number added to the data that is transmitted and received by the receiver and notifies the second sequence number to a target base station; and a transmitter that transmits the data to which the second sequence number is added to the mobile station.